Glass forming plunger



Aug. 24, 1965 .1. J. ToRoK GLASS FORMING PLUNGER 2 Sheets-Sheet l FiledMay 17, 1961 WATER coNTAcTlNG METAL SURFAC. HEAT FLom/[aTu/Ftz/HrzjxloooTEMPERATURE RISC p HEAT now @Tu/FTf/Hvzjx :ooo

Aug. 24, 1965 J. J. TOROK @202,498

GLASS FORMING PLUNGER Filed May l?. 1961 2 Sheets-Sheet 2 2o ao eo soHEAT FLOW [aTu/FT/Halxlooo L1() 600 BOO [OOO lOC PLUNGER SURFACETEMPERATURER (Com-ACTING SURFACE) F l c. 6

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PLUNGER SURFACE. TEMPE :aA-ruvs INVENTOR JuLrus J. TOROK BY d?. AQ@

A TTORNE YS United States Patent Office ZAQ Patented Aug. 2d, ld

3,292,493 GLASS FGREEENG Pil-UNSER Julius J. Toi-oir, Toledo, Shin,assigner', by mesne assignments, to @wens-illinois Glass Company,Toledo, (Ehio, a corporation ol @hin lFiled May i7, lldl, Ser. No.lltltld l Claims. (Cl. dS-Sm This application is a continuationwin-partof my cepending applications, Serial Numbers 763,384 and 763,351, filedSeptember 25, i958, which are now Patents 3,054,220 and 3,078,696,respectively.

This invention relates to the forming of glass articles and particularlyto the molding by pressing of a glass article having a base and a llangeextending around the periphery of the base and forming an angletherewith.

ln making of glass articles, such as the face plates of televisionpicture tubes and glass block halves which have a base and a angeextending around the periphery of the base and forming an angle with thebase, a gobern glass is placed in a mold having an internal moldingsurface corresponding to the external configuration of the article whichis to be formed and a plunger is moved downwardly to press and form .theglass. The plunger has an external molding surface corresponding to theinternal configuration of the glass article which is to be formed.

ln the making of glass articles in accordance with such a method it isessential that the forming surfaces of the mold and the plunger bemaintained within predetermined temperatures. If the forming surfaceshave too high a temperature the glass will stick. This will necessitatea stoppage of the forming equipment in order to repair the damage causedby sticking. If the glass-forming surfaces are at too low a temperature,a crizzle or wrinkle will be formed in the glass article. Either oithese conditions is obviously undesirable and it is necessary that theglassforming surfaces be operated at temperatures between the twoextremes in order that glass articles may be successfully formed at lowcost.

En order to achieve this, it has been necessary to cool the surfaces ofthe mold, opposite the molding surfaces, with water.

ln the design of plungers of this type, it has been cornrnonly assumedthat the internal surface of the plunger which is contacted by the wateris at the same temperature as the water. In order to increase theedectiveness of the water which is used for cooling the plunger, it hasbeen thought necessary to either increase the amount of water beingcirculated or reduce the thickness of the plunger at that particulararea as disclosed in my copending applications Serial Nos. 763,384, nowPatent 3,054,220, and 763,351, tiled September 25, 1958.

Even with the best possible design, it has been found that there is amaximum speed beyond which the plunger cannot be operated withoutexceeding the working llimits of temperature. If the speed of operationis increased beyond this point, the temperature of the plunger rises inan unpredictable manner resulting in sticking of the glass.

It is an object of this invention to provide a plunger which may beoperated at higher speed than has been heretofore possible for the samepart being made out of the same glass.

It is a further object of the invention to provide such a plungerwherein the increased production can be obtained at minimum cost.

Basically, the invention comprises providing a peripheral groove at thearea of juncture of the llange portion and base portion of the plungeron the inner surface thereof and a plurality of inwardly extending ns orribs in the groove which are thermally bonded to the surface of theplunger and extend int-o the path of the cooling liquid.

l have recognized for the irst time that, at high speeds, the innersurface of the plunger is not at the temperature of the liquid and thatlrn boiling occurs at the inner surface which results in a loss ofcontrol of temperature. To eliminate this condition, under particularoperating conditions, according to the invention, the heat flow througha particular area is determined and then suicient extended surface inthe form of fins or ribs is provided to reduce the heat flow density atthat particular area below that point at which a film boiling will occurso that the outer surface of the plunger will operate within the properlimits (nucleate boiling) oi temperature.

ln the drawings:

FlG. l is a sectional elevational View of a glass forming apparatusembodying the invention.

FIG. 2 is a fragmentary perspective of a portion of the plunger shown inFlG. l.

PEG. 3 is a view similar to FIG. 2 showing a modilied form of plunger.

FIG. 4 is a view similar to FIG. 2 showing a further modified form ofplunger.

FIG. 5 is a curve of temperature rise versus heat flow in a plunger.

FG. 6 is a curve of heat low versus plunger glass contacting surfacetemperature.

FIG. 7 is a curve of heat ilow versus temperature rise in a plunger.

FlG. 8 is a curve of heat flow versus plunger surface temperature.

Referring to FlG. l, a mold lil is provided into which a gob of glass isdeposited by suitable means well known in the art and thereafter plungeril is brought downwardly into contact with the glass to press and formthe glass article.

As shown in FIG. l, mold Il@ comprises a base section l2 and aperipheral section i3 dehning an internal molding surface le which has aconliguration corresponding to the external configuration of the glassarticle which is to be formed. Peripheral section i3 includes aninwardly extending eripheral lip l5 which defines the upper end of theflange which is to be formed on the glass article.

Plonger ll includes a base portion lo and a flange portion i7 and ismounted on a head 18 by bolts i9 threaded into ilange portion 17 of theplunger ll. A gasket Ztl is interposed between the upper end of flangeportion 17 of plunger lll and head ld. Head l is adapted to be movedupwardly and downwardly by a suitable mechanism (not shown) known in theart, such as a hydraulic ram.

The specific construction of plunger ll may vary but preferably is ofthe type disclosed and claimed in my copending application, Serial No.763,351, titled Forming Glass Articles. ln such a plunger ll, a baseportion lo is of substantially uniform thickness and flange portion l?extends around the periphery of said base portion and forms an angle notexceeding thereto. A peripheral groove 2l is provided in the area ofjuncture of the base portion lo and ilange portion i7 on lthe side ofthe plunger opposite the mold-ing surface. ln addition, a .slot 22 isprovided in the upper end of flange portion l7. Slot 22 is preferablyfilled with an insulating material 23 such as asbestos.

Liquid coolant is directed against the base of groove 2l at the area ofjuncture of base portion 16 and flange portion i7 and a rotary motion isimparted to the liquid coolant. ln addition, the liquid coolant isguided at a uniform rate along the surface of base portion 16 oppositethe molding surface of the plunger from the periphery toward the centerand is thereafter removed from the plunger.

As shown in FIGS. 1 and 2, a distributor 2S is provided between head land plunger 1l and comprises a circular plate 26 and a hub Z7 at thecenter of the enoaaes plate.' Bolts 2S extend through circumferentiallyspaced bosses 29 to support distributor 25 on the lower end of head 13.A lip 26a is formed on the periphery of plate and extends upwardly intocontact with gasket 2t?. Liquid coolant is forced under pressure throughcircumferentially spaced vertical openings Si? in head 18 into the space4t) between plate Z6 and lower end of the head. A plurality of nozzlesis provided in the periphery of the distributor. Each nozzle comprises aplug 31 threaded into an opening-in the distributor. with a nozzleopening 32 which has its axis inclined horizontally to a radial planeintersecting the axis of plunger In this fashion, a plurality of streamsor jets of liquid coolant are directedrat the area of juncture of thekperiphery of base portion 16 and ange portion'll of plunger 11, thatis, into groove 2.1.V An O-ring type gasket 33 is provided on the upperend of hub 27 to provide a seal and prevent the liquid coolant frompassing from the inlet directly to the outlet opening 34 in head 18.

A disc 3d is provided below distributor Z5 and includes a sleeve 36extending upwardly into hub 27. The upper end of sleeve 36 is spacedfrom the base of the opening of the hub in which it extends so that disc35 has limited reciprocating movement relative to hub 27 and, in turn,distributor 25. Bolts 37 locked in position by lock nuts 3S are providedat circumferentially spaced points along the periphery of disc V35 andextend through the disc into contact with the inner surface of baseportion f6. By this arrangement, the lowerrnost position of Vdisc, 35 isadjusted so that the disc is always out of contact with the innersurface of base portion 16.

In operation, gobs of glass are periodically fed to mold 14 and plunger16 is moved downwardly into Contact with each gob to form the glassarticle.

During the operation of the forming equipment, liquid coolant is forcedunder pressure through openings Y into the space between the lower endof head 18 and distributor 25. Coolant is then directed in a pluralityof streams or jets at the area of juncture ofthe base portion 16 andflange portion 17. Since the axes of the jets are at an angleto a radialline intersecting the axis of the plunger, a rotary motion is impartedto the coolant. The liquid coolant fillsV the space ttl between theundersurface of plate 2o and the upper surface of disc 35 forcing discdownwardly and bringing the ends of bolts into contactwvith the innersurface 16a of base portion 16. The restricted ow through space 39between disc 3S and base portion 16 causes a small pressure drop y whichproduces a differential pressure between the space 4i) and the space41insuring that the disc 35 is urged downwardly into proper positionwith respect' to the surface. p

The undersurface of disc 35 is so shaped relative to the surface of baseportion 16 of plunger 11 that the liquid, as it ows from the peripheryof the base portion to the center thereof, flows at a constant velocity.`In other words, the cross-sectional area ofthe space #i1VV betweenuthelower or undersurface of disc 35 and the inner surface of base portion16 is such that it increasesv in size from the periphery to the centerso that a constant velocity of liquid will be permitted to flow. Theliquid coolant isr withdrawn through sleeve 36 and outlet 34.

The surface of the plunger 16 against which the coolant is directed ispreferably roughened in order to ,obtain the best possible heattransfer. The roughening may be achieved by knurls or in any othersuitable manner such as ribs. Ihe roughening should be suflicient toinsure heat transfer but not so deep as to form stagnant pockets ofcooling. Y

` The apparatus heretofore-describedis similar to that disclosed andclaimed in my copending application Serial No. 763,384. y l

' According to the invention, the surface Si) of the groove 21 i1"-formed with extended surfaces in the form-ofl Each plug is formed Yinner surface of the plunger.

outer surfaces'o'f the plunger.

4x. integral iinsdl which are circumfercntialiy and radially spaced andextend into the path of the Vliquid coolant as shown in FliG. 2. Thefins 51 reduce the heat flow den- V sity at the groove'resulting in acooler operating surface on the inner surface at the groove. As aresult, the plunger can be operated at a higher rate without exceedingthe temperature Operating limit.

Instead of utilizing isolated ns 51, peripherally extending grooves 53Vmay be provided in the groove as shown in HG. 3. Mternatively, ribs 54embedded or thermally bonded in the groove can be provided as shown r inFIG. 4.

The theory upon which the invention is based can be morerreadilyunderstood by reference to FlGS. 5 to 8. FG. 5 is a curve of temperaturerise ofthe Water cooled surface versus heat flow. The temperature riseis the difference between the temperature yof the inner surface of theplungerV and the water being circulated over the Since the thermalconductivity of water is very low, with increased heat ow thetemperature rise in the water follows the curve shown in FG. 5 until apoint is reached at which the temperature rise is very rapid. l haveldetermined that this occurs because of theV formation of bubbles due toboiling at the inner surface of the plunger. YAs theV nucleate boilingincreases, a lm of bubbles isforined completely separating the waterfrom the surface of the plunger resulting in ahigh temperature rise inthe surface of the plunger. By reducing thespeed of operation of thcplunger, the'heat iiow may be reduced sufficiently to prevent theuncontrolled temperature rise of the plunger.

f have found that the limiting speed of operation of the plunger isdetermined by-occurrence of iilm boiling. At any speed at which filmboiling occurs, it can be eliminated by applying extended surfaces inthe form of fins or ribs at the areas of high heat density. The amountlY of heat transferred to the water will be increased.

As shown in FIG. 6, which Vis a curve of heat flow versus outer plungersurface temperature, if the glass contacting surface temperature is 675F., 80,00() Etufs must be dissipated per square inch. According to FIG.5, this will .result in film boiling.V However, if the surface at whichthis high heat density occurs is extended, Yas by ribs or Vfins,the'heat flow per square `inch isreduced below 80,660 B.tr.u.s. Forexample, if the area is doubled, then the heat flow per square unit ofarea will be 40,090 B.t.u.s per square inchwhich, as shown in FiG. 5, is`well withinV or below the film boiling point X so that the plunger willoperate satisfactorily at that speed.

FIG. 7 .shows two curves. Curve C represents the heat flow versustemperature rise between the inner and -Curve D represents the heat flowversus temperature rise between the temperature 'of the inner surface ofthe .plunger and the Water temperature. Y

v Vifi. 8 is a composite between FlGS. 6 and 7. Curve B shows the curveof FiG. 6 when the surfaceV is ex- ;tended by ribs or fins resulting ina decrease in heat flow density. rCurve E is the'heat'ilow versustemperay ture riserdiferencerbetween inner and outer surfaces. It can beseen'that a plunger with extended surfaces, represented by curve B',operates below the points Where control of plunger temperature is lost.

*In the application of the corrugated surfaces, it is preferred tokprovide the surfaces of suicient area to accomplish the desiredreduction in heat ilow` density. In addition, the surfaces can be of amore highly conductive lmaterial to give a lesser drop in temperature.

. In this connection, it is preferred to proyide a'plurality of shortribs'and fins rather" than a few longer ribs or fins. On the contrary,longer ns or ribs are to be avoid-V ed since they result in too greatjatemperature drop Y lin theribs Vso that the temperature differencebetween the water and the surface of the plunger is less resulting in alesser transfer of heat.V A

Thus, by adding the fins or ribs, the threshold ternperature of nucleateboiling is not exceeded so that the plunger can be operated at a higherrate than has been heretofore possible without the use of the extendedsurfaces in the form of fins or ribs.

It should be appreciated that the exact point of film boiling cannot bedefinitely established in advance since it also depends on other factorssuch as gases in the Water which tend to lower the film boiling point,surface tension wetability, wherein a lesser wetting produces a lower lmboiling point, and pressure of water, wherein a lower pressure resultsin a lower film boiling point.

I claim:

1. In an apparatus for forming a glass article having one portionconnected to the other by a curved portion of small radius wherein saidapparatus includes a mold and a plunger which is moved relative to themold to press the goh of glass, the internal surface of the mold havinga configuration corresponding to the external surface of the articlewhich is to be formed, said plunger having an external surfacecorresponding to the internal surface of the article to be formed andcomprising a base portion and a flange portion connected to said baseportion by a sharply curved portion at the area of juncture with thehase portion and extending upwardly from the base portion, said plungerhaving an internal surface and means for circulating a liquid coolantacross said internal surface to continuously remove heat and cool theplunger, said plunger being formed with a peripheral groove therein inthe inner surface thereof opposite the molding surface thereof at thecurved portion, the improvement for eliminating film boiling at theinner surface of the plunger at the groove which comprises meansdeiining a plurality of extended thermally bonded surfaces on theinternal surface of the plunger at d said peripheral groove, saidsurfaces extending into the path of the liquid coolant.

2. The combination set forth in claim l wherein said extended surfacescomprise a plurality of peripherally extending continuous ins thermallybonded to the internal surface of the plunger at said groove.

3. The combination set forth in claim l wherein said extended surfacescomprise a plurality of integral circumferentially isolated finspositioned on the internal surface of the plunger at said groove andextending into the path of the liquid coolant.

4. In an apparatus for forming a glass article having one portionconnected to the other by a curved portion of small radius wherein saidapparatus includes a mold and a plunger which is moved relative to themold to press the gob of glass, the internal surface of the mold havinga configuration corresponding to the external surface of the articlewhich is to be formed and the external surface of the plunger having aconguration corresponding to the internal surface of the article to beformed, said plunger having an internal surface and means forcirculating a liquid coolant across said internal surface tocontinuously remove heat and cool the plunger, the improvementcomprising a plurality of extended thermally bonded surfaces on theinternal surface of the plunger at the curved portion thereof, saidsurfaces extending into the path of the liquid coolant.

References Cited hy the Examiner UNITED STATES PATENTS 2,688,823 9/54Weber 65-362 3,054,220 9/62 Torok 65-362 DONALL H. SYLVESTER, PrimaryExaminer.

1. IN AN APPARATUS FOR FORMING A GLASS ARTICLE HAVING ONE PORTIONCONNECTED TO THE OTHER BY A CURVED PORTION OF SMALL RADIUS WHEREIN SAIDAPPARATUS INCLUDES A MOLD AND A PLUNGER WHICH IS MOVED RELATIVE TO THEMOLD TO PRESS THE GOB OF GLASS, THE INTERNAL SURFACE OF THE MOLD HAVINGA CONFIGURATION CORRESPONDING TO THE EXTERNAL SURFACE OF THE ARTICLEWHICH IS TO BE FORMED, SAID PLUNGER HAVING AN EXTERNAL SURFACECORRESPONDING TO THE INTERNAL SURFACE OF THE ARTICLE TO BE FORMED ANDCOMPRISING A BASE PORTION AND A FLANGE PORTION CONNECTED TO SAID BASEPORTION BY A SHARPLY CURVED PORTION AT THE AREA OF JUNCTURE WITH THEBASE PORTIN AND EXTENDING UPWARDY FROM THE BASE PORTION, SAID PLUNGERHAVING AN INTERNAL SURFACE AND MEANS FOR CIRCULATING A LIQUID COOLANTACROSS SAID INTERNAL SURFACE TO CONTINUOUSLY REMOVE HEAT AND COOL THEPLUNGER, SAID PLUNGER BEING FORMED WITH A PERIPHERAL GROOVE THEREIN INTHE INNER SURFACE THEREOF OPPOSITE THE MOLDING SURFACE THEREOF AT THECURVED PORTION, THE IMPROVEMENT FOR ELIMINATING FILM BOILING AT THEINNER SURFACE OF THE PLUNGER AT THE GROOVE WHICH COMPRISES MEANSDEFINING A PLURALITY OF EXTENDED THERMALLY BONDED SURFACES ON THEINTERNAL SURFACE OF THE PLUNGER AT SAID PERIPHERAL GROOVE, SAID SURFACESEXTENDING INTO THE PATH OF THE LIQUID COOLANT.